Tính

Bài 8:
a.2x².(x-1+3x).(x²-x-5).(3-x²)
b.3x.(x-2-5x).(1-x-8).(x²-3)
Bài 9:
a.(-x+1).(x²-2-1-x³-x²)
b.x-8x².(2x-1+2x-2x²)
Bài 10:
a.(-3x+1).(x²+1+3x-1)
b.(4x-1).(3x+1-12x²+1)